It is known that a conventional typical tool changer is composed of a tool magazine having a plurality of tool holders holding tools, a magazine driving mechanism driving the tool magazine to move one of the tool holders to a tool change position, a tool changing mechanism changing a tool attached to a spindle with a tool positioned at the tool change position, and a tool change control part controlling operations of the magazine driving mechanism and tool changing mechanism (see Japanese Unexamined Patent Application Publication No. H8-318443).
In such a tool changer, attachment of tools to the tool holders and detachment of tools from the tool holders, which are set-up operations, are manually performed by an operator. In the case of a tool magazine having a number of tool holders, a tool attachment/detachment position for the attachment and detachment of tools by the operator is set and a manual operation device for inputting into the tool change control part an operation signal for selectively moving a particular one of the plurality of tool holders to the tool attachment/detachment position is provided.
In such a tool changer, the operator designates a tool holder to be operated through the manual operation device, whereby an operation signal for moving the designated tool holder to the tool attachment/detachment position is transmitted from the manual operation device to the tool change control part. Under control by the tool change control part, the magazine driving mechanism is driven and thereby the designated tool holder is moved to the tool attachment/detachment position. Thus, the operator can call an intended tool holder to the tool attachment/detachment position through this operation and can attach a tool to the tool holder or detach a tool from the tool holder.
By the way, the set-up operation includes other types of operations, such as an operation of, when a new machining operation that has not been executed in the machine tool is performed using newly set tools, attaching the newly set tools to the tool holders, which is a set-up operation performed before the machining operation is started, and an operation of, when a tool has reached its wear limit through machining, exchanging the tool which has reached its wear limit with a new one. Note that the tool exchange timing is typically managed by keeping track of a cumulative machining time of each tool. Each tool has an empirically set limit machining time that is regarded as its wear limit, and the exchange timing for each tool is set based on its limit machining time and a tool which has reached its exchange timing is exchanged by the operator.
Further, a numerical controller of a machine tool typically stores therein a plurality of NC programs and multiple kinds of machining operations corresponding to the NC programs are executed in the machine tool. Therefore, a plurality of tools which are used in the machining operations are previously stored into the tool magazine; some of the tools are shared by several machining operations and others are used in one machining operation.
Because of these backgrounds, conventionally, a tool which has reached its machining limit is exchanged not only while the machine tool is stopped but also while a machining operation is performed. That is, the tool magazine holds tools which are not used in the machining operation; therefore, exchanging such a tool during the machining operation does not affect the machining operation.